Integrated circuit (IC) processes include dry etching to form a plurality of metal layers. In one particularly process, a platinum (Pt) layer is defined to provide a pair of electrodes, such as for certain Microelectromechanical systems (MEMS) devices. Pt is generally ion milled or wet etched, but this is either expensive and/or difficult to control. Alternatively Pt can be dry etched, such as by a plasma etch, using a photoresist mask and an etch gas such as Ar/Cl2, Cl2/BCl3 or Cl2/HBr.
During Pt dry etch, a Pt-containing sidewall polymer defect (metal within the polymer, referred to herein as a metal/polymer sidewall defect) can grow on the edges of the photoresist-protected Pt film and remain at the photoresist edge after photoresist strip. Due to its mixed composition, this metal/polymer sidewall defect is known to be difficult to remove. Known solutions to remove the metal/polymer sidewall defect are wet chemical strip, ashing, and plasma-etching.